linux-kernel - [PATCH] regmap-i2c: Use i2c block command only if register value width is 8 bit

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Message-Id: <1466532263-23659-1-git-send-email-linux@roeck-us.net>
Date:	Tue, 21 Jun 2016 11:04:23 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Mark Brown <broonie@...nel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
	Markus Pargmann <mpa@...gutronix.de>
Subject: [PATCH] regmap-i2c: Use i2c block command only if register value width is 8 bit

Chips with 16-bit registers don't usually work well with I2C block
commands. For example, neither the LM75 datasheet nor the TMP102 datasheet
mentions block command support, and in fact it does not work for any of
those chips. Also, it is not clear how the block command would handle
16-bit SMBus operations in the fist place, since the data format associated
with those commands is either little endian or big endian, which requires
some kind of conversion to or from host byte order.

Only use i2c block commands if both register and value width is 8 bit.

Fixes: 29332534e2b6 ("regmap-i2c: Add smbus i2c block support")
Cc: Markus Pargmann <mpa@...gutronix.de>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 drivers/base/regmap/regmap-i2c.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/regmap/regmap-i2c.c b/drivers/base/regmap/regmap-i2c.c
index 1a8ec3b2b601..4735318f4268 100644
--- a/drivers/base/regmap/regmap-i2c.c
+++ b/drivers/base/regmap/regmap-i2c.c
@@ -259,7 +259,7 @@ static const struct regmap_bus *regmap_get_i2c_bus(struct i2c_client *i2c,
 {
 	if (i2c_check_functionality(i2c->adapter, I2C_FUNC_I2C))
 		return &regmap_i2c;
-	else if (config->reg_bits == 8 &&
+	else if (config->val_bits == 8 && config->reg_bits == 8 &&
 		 i2c_check_functionality(i2c->adapter,
 					 I2C_FUNC_SMBUS_I2C_BLOCK))
 		return &regmap_i2c_smbus_i2c_block;
-- 
2.5.0